President Barack Obama and Russian President Dmitry Medvedev chat following the conclusion of their bilateral meeting March 26 at the Nuclear Security Summit Seoul, South Korea.

At a medical device company in San Diego, Romney called the president's comments -- captured Monday on an open microphone -- "an alarming and troubling development" as part of a longer wind-up about the importance of missile defense and standing by our allies.

“This weekend, the president happened to be somewhere where the microphone was left open. You may have heard that. It can be revealing, in this case, it was. He was speaking with Mr. Medvedev, of Russia. And he said, ‘This is my last election, I can be more flexible after the election is over,'" Romney started.

"Now when the president of the United States is speaking with the leader of Russia saying he can be more flexible after the election, that is an alarming and troubling development," Romney said. "There's no time for our president to be pulling his punches with the American people and not telling us what he's intending to do with regards to our missile defense system; with regards to our military might and with regards to our commitment to Israel; and with regards to our absolute conviction that Iran must have a nuclear weapon."

Obama's comments were captured at the very beginning of the photo opportunity after the the bilateral meeting between the president and Medvedev, when the two leaders were leaned over and speaking to each other.

"This is my last election," Obama was heard saying, "After my election I have more flexibility."

Medvedev responded that he would "transmit this information to Vladimir," meaning Vladimir Putin, the president-elect of Russia.

A Russian journalist's recording indicates the two leaders were talking about missile defense, a touchy area in U.S.-Russian relations.

Before Romney's remarks had concluded, President Obama's campaign pushed back at the former Massachusetts governor's criticism.

“Once again Governor Romney is undermining his credibility by distorting the President’s words," Obama campaign spokesman Ben LaBolt said in a statement. "Governor Romney has been all over the map on the key foreign policy challenges facing our nation today, offering a lot of chest thumping and empty rhetoric with no concrete plans to enhance our security or strengthen our alliances."

Romney delivered his attack of the president during a speech that began with a critique of the President's health care law. Standing before a sign reading "Repeal and Replace Obamacare," Romney said there were "a lot of reasons not to like Obamacare," and outlined a number of his issues with the law, but stopped short of his usual direct call for the bill's repeal.

In his more than twenty minutes of remarks, Romney also never mentioned the Supreme Court case beginning today that could decide the law's fate well before the November election.